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Abstract:

Provided is a method of manufacturing a vertical LED, the method including
the steps of: preparing a sapphire substrate; forming a light emitting
structure in which an n-type nitride semiconductor layer, an active
layer, and a p-type nitride semiconductor layer are sequentially
laminated on the sapphire substrate; forming a p-electrode on the p-type
nitride semiconductor layer; forming a structure support layer on the
p-electrode; removing the sapphire substrate through an LLO (laser
lift-off) process; isolating the light emitting structure into unit LED
elements through an ISO (isolation) process; and forming an n-electrode
on each of the n-type nitride semiconductor layers of the isolated light
emitting structures.

Claims:

1. A method of manufacturing a vertical LED, comprising the steps
of:preparing a sapphire substrate;forming a light emitting structure in
which an n-type nitride semiconductor layer, an active layer, and a
p-type nitride semiconductor layer are sequentially laminated on the
sapphire substrate;forming a p-electrode on the p-type nitride
semiconductor layer;forming a structure support layer on the
p-electrode;removing the sapphire substrate through an LLO (laser
lift-off) process;isolating the light emitting structure into unit LED
elements through an ISO (isolation) process; andforming an n-electrode on
each of the n-type nitride semiconductor layers of the isolated light
emitting structures.

2. The method according to claim 1 further comprising the step of:forming
an insulating film on the side surfaces of the isolated light emitting
structures, after the isolating of the light emitting structure.

3. The method according to claim 1 further comprising the step of:forming
a reflecting film on the side surfaces of the isolated light emitting
structures, after the isolating of the light emitting structure.

4. A method of manufacturing a vertical LED, comprising the steps
of:preparing a sapphire substrate;forming a light emitting structure in
which an n-type nitride semiconductor layer, an active layer, and a
p-type nitride semiconductor layer are sequentially laminated on the
sapphire substrate;forming buffer films on portions of the surface of the
p-type nitride semiconductor layer corresponding to element isolation
regions;forming a p-electrode on the resulting structure having the
buffer films formed thereon;forming a structure support layer on the
resulting structure having the p-electrode formed thereon;removing the
sapphire substrate through an LLO process;isolating the light emitting
structure into unit LED elements through an ISO process; andforming an
n-electrode on each of the n-type nitride semiconductor layers of the
isolated light emitting structures.

5. The method according to claim 4, wherein the p-electrode is formed on
the surface of the p-type nitride semiconductor layer excluding the
portions on which the buffer films are formed.

6. The method according to claim 4, wherein the buffer films are composed
of a non-conductive material.

7. The method according to claim 6, wherein the non-conductive material is
one or more selected form the group consisting of photoresist, polyimide,
epoxy, and dielectric.

8. The method according to claim 4 further comprising the step of:forming
an insulating film on the side surfaces of the isolated light emitting
structures after the isolating of the light emitting structure.

9. The method according to claim 4 further comprising the step of:forming
a reflecting film on the side surfaces of the isolated light emitting
structures after the isolating of the light emitting structure.

10. A method of manufacturing a vertical LED, comprising the steps
of:preparing a sapphire substrate;forming a light emitting structure in
which an n-type nitride semiconductor layer, an active layer, and a
p-type nitride semiconductor layer are sequentially laminated on the
sapphire substrate;performing a first ISO process for isolating the light
emitting structure into unit LED elements such that portions of the light
emitting structure corresponding to element isolation regions remain with
a predetermined thickness on the sapphire substrate;forming a p-electrode
on the surface of the p-type nitride semiconductor layer corresponding to
each unit LED element region;forming a structure support layer on the
p-electrode;removing the sapphire substrate through an LLO
process;performing a second ISO process for completely isolating the
light emitting structure into unit LED elements by removing the remaining
portions of the light emitting structure corresponding to the element
isolation regions; andforming an n-electrode on each of the n-type
nitride semiconductor layers of the isolated light emitting structures.

11. The method according to claim 10 further comprising the step
of:forming a first insulating film on the side surfaces of the isolated
light emitting structures after the performing of the first ISO process.

12. The method according to claim 11 further comprising the step
of:forming a second insulating film on the side surfaces of the isolated
light emitting structures after the performing of the second ISO process.

13. The method according to claim 10 further comprising the step
of:forming a first reflecting film on the side surfaces of the isolated
light emitting structures after the performing of the first ISO process.

14. The method according to claim 11 further comprising the step
of:forming a second reflecting film on the side surfaces of the isolated
light emitting structures after the performing of the second ISO process.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims the benefit of Korean Patent Application No.
10-2007-0120260 filed with the Korea Intellectual Property Office on Nov.
23, 2007, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a method of manufacturing a
vertical light emitting diode (LED), which can prevent the damage of a
light emitting structure during an LLO (laser lift-off) process for
removing a sapphire substrate.

[0004]2. Description of the Related Art

[0005]Generally, a nitride-based semiconductor LED is grown on a sapphire
substrate, but the sapphire substrate is a rigid nonconductor and has
poor thermal conductivity. Therefore, there is a limitation in reducing
the manufacturing costs by reducing the size of a nitride-based
semiconductor LED, or improving the optical power and chip
characteristic. Particularly, because the application of a high current
is essential for achieving high power LED, it is important to solve a
heat-sink problem of the LED. To solve this problem, there has been
proposed a vertical LED in which a sapphire substrate is removed using an
LLO technique.

[0006]Now, a conventional method of manufacturing a vertical LED will be
described with reference to FIGS. 1A to 1F.

[0008]First, as shown in FIG. 1A, a light emitting structure 110 is formed
on a transparent substrate 110 such as sapphire. The light emitting
structure 110 includes an n-type nitride semiconductor layer 112, a
GaN/InGaN active layer 114 with a multi-quantum well structure, and a
p-type nitride semiconductor layer 115, which are sequentially laminated.

[0009]As shown in FIG. 1B, photoresist patterns PR for defining a desired
size of unit LED elements are formed on the p-type nitride semiconductor
layer 115.

[0010]Subsequently, as shown in FIG. 1C, the light emitting structure 110
is isolated into unit LED elements through an ISO (isolation) process
using dry etching such as ICP (inductive coupled plasma) or layer, with
the photoresist patterns being set to an etching mask. Then, the
photoresist patterns are removed.

[0011]Although not shown, after the light emitting structure 110 is
isolated into unit LED elements, an insulating film or reflecting film
may be formed on the side surfaces of the isolated light emitting
structures 110. The insulating film or reflecting film can be omitted
depending on the characteristics of LED and process conditions.

[0012]Next, as shown in FIG. 1D, a p-electrode 140 is formed on each of
the isolated light emitting structures 110. Then, as shown in FIG. 1E, a
structure support layer 160 is formed on the p-electrode 140.

[0013]Subsequently, as shown in FIG. 1F, the substrate 110 is removed
through the LLO process. In the LLO process, when an energy of about 700
mJ/cm2 is applied at the normal temperature in an arrow direction,
the energy is absorbed at the interface between the substrate 100 and the
light emitting structure 110 such that the bonded surface of the light
emitting structure 110 is thermally discomposed, and the substrate 100
and the light emitting structure 110 are then separated from each other.

[0014]Then, although not shown, an n-electrode is formed on each of the
n-type nitride semiconductor layers 112 which are exposed by the removing
of the substrate, thereby forming vertical LEDs.

[0015]In the conventional method of manufacturing a vertical LED, when the
LLO process for removing the substrate is performed, cracks occur at the
edge of the light emitting structure 100, as indicated by `A` in FIG. 2.
Then, defects may occur in the LED. FIG. 2 is a photograph showing the
problem of the vertical LED manufactured according to the conventional
method.

[0016]Further, a crack may also occur in the insulating film or reflecting
film formed on the side surfaces of the isolated light emitting
structures or the adhesion therebetween may be degraded during the LLO
process.

[0017]Therefore, when a vertical LED is manufactured according to the
conventional method, the characteristic and reliability of the vertical
LED are degraded because of the above-described problems.

SUMMARY OF THE INVENTION

[0018]An advantage of the present invention is that it provides a method
of manufacturing a vertical LED, which can prevent the damage of a light
emitting structure during an LLO process for removing a sapphire
substrate.

[0019]Additional aspects and advantages of the present general inventive
concept will be set forth in part in the description which follows and,
in part, will be obvious from the description, or may be learned by
practice of the general inventive concept.

[0020]According to an aspect of the invention, a method of manufacturing a
vertical LED comprises the steps of: preparing a sapphire substrate;
forming a light emitting structure in which an n-type nitride
semiconductor layer, an active layer, and a p-type nitride semiconductor
layer are sequentially laminated on the sapphire substrate; forming a
p-electrode on the p-type nitride semiconductor layer; forming a
structure support layer on the p-electrode; removing the sapphire
substrate through an LLO (laser lift-off) process; isolating the light
emitting structure into unit LED elements through an ISO (isolation)
process; and forming an n-electrode on each of the n-type nitride
semiconductor layers of the isolated light emitting structures.

[0021]Preferably, the method further comprises the step of forming an
insulating film or reflecting film on the side surfaces of the isolated
light emitting structures, after the isolating of the light emitting
structure.

[0022]According to another aspect of the invention, a method of
manufacturing a vertical LED comprises the steps of: preparing a sapphire
substrate; forming a light emitting structure in which an n-type nitride
semiconductor layer, an active layer, and a p-type nitride semiconductor
layer are sequentially laminated on the sapphire substrate; forming
buffer films on portions of the surface of the p-type nitride
semiconductor layer corresponding to element isolation regions; forming a
p-electrode on the resulting structure having the buffer films formed
thereon; forming a structure support layer on the resulting structure
having the p-electrode formed thereon; removing the sapphire substrate
through an LLO process; isolating the light emitting structure into unit
LED elements through an ISO process; and forming an n-electrode on each
of the n-type nitride semiconductor layers of the isolated light emitting
structures.

[0023]Preferably, the p-electrode is formed on the surface of the p-type
nitride semiconductor layer excluding the portions on which the buffer
films are formed.

[0024]Preferably, the buffer films are composed of a non-conductive
material. As for the non-conducive material, photoresist, polyimide,
epoxy, and dielectric may be used.

[0025]According to a further aspect of the invention, a method of
manufacturing a vertical LED comprises the steps of: preparing a sapphire
substrate; forming a light emitting structure in which an n-type nitride
semiconductor layer, an active layer, and a p-type nitride semiconductor
layer are sequentially laminated on the sapphire substrate; performing a
first ISO process for isolating the light emitting structure into unit
LED elements such that portions of the light emitting structure
corresponding to element isolation regions remain with a predetermined
thickness on the sapphire substrate; forming a p-electrode on the surface
of the p-type nitride semiconductor layer corresponding to each unit LED
element region; forming a structure support layer on the p-electrode;
removing the sapphire substrate through an LLO process; performing a
second ISO process for completely isolating the light emitting structure
into unit LED elements by removing the remaining portions of the light
emitting structure corresponding to the element isolation regions; and
forming an n-electrode on each of the n-type nitride semiconductor layers
of the isolated light emitting structures.

[0026]Preferably, the method further comprises the step of forming a first
insulating film or first reflecting film on the side surfaces of the
isolated light emitting structures after the performing of the first ISO
process.

[0027]Preferably, the method further comprises the step of forming a
second insulating film or second reflecting film on the side surfaces of
the isolated light emitting structures after the performing of the second
ISO process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]These and/or other aspects and advantages of the present general
inventive concept will become apparent and more readily appreciated from
the following description of the embodiments, taken in conjunction with
the accompanying drawings of which:

[0030]FIG. 2 is a photograph showing the problem of a vertical LED
manufactured according to the conventional method;

[0031]FIGS. 3A to 3F are process diagrams sequentially showing a method of
manufacturing a vertical LED according to a first embodiment of the
invention;

[0032]FIG. 4 is a process diagram for explaining a modification of the
method of manufacturing a vertical LED according to the first embodiment
of the invention;

[0033]FIG. 5 is a process diagram for explaining a method of manufacturing
a vertical LED according to a second embodiment of the invention; and

[0034]FIGS. 6A to 6E are process diagrams sequentially showing a method of
manufacturing a vertical LED according to a third embodiment of the
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035]Reference will now be made in detail to the embodiments of the
present general inventive concept, examples of which are illustrated in
the accompanying drawings, wherein like reference numerals refer to like
elements throughout. The embodiments are described below in order to
explain the present general inventive concept by referring to the
figures.

[0036]Hereinafter, a method of manufacturing a vertical LED according to
the present invention will be described in detail with reference to the
accompanying drawings.

First Embodiment

[0037]Referring to FIGS. 3A to 3F, a method of manufacturing a vertical
LED according to a first embodiment of the invention will be described.

[0038]FIGS. 3A to 3F are process diagrams sequentially showing a method of
manufacturing a vertical LED according to a first embodiment of the
invention.

[0039]First, as shown in FIG. 3A, a light emitting structure 110 composed
of a nitride-based semiconductor layer is formed on a transparent
substrate 100 such as sapphire. The light emitting structure 110 includes
an n-type nitride semiconductor layer 112, a GaN/InGaN active layer 114
with a multi-quantum well structure, and a p-type nitride semiconductor
layer 115, which are sequentially laminated.

[0040]The n-type and p-type nitride semiconductor layer 112 and 115 and
the active layer 114 may be formed of a nitride semiconductor material
having a compositional formula of AlxInyGa.sub.(1-x-y)N (here,
0≦x≦1, 0≦y≦1, and 0≦x+y≦1) and
can be formed through a well-known nitride deposition process such as
MOCVD (Metal Organic Chemical Vapor Deposition).

[0041]The active layer 114 may be formed of one quantum-well layer or with
a double-hetero structure.

[0042]Subsequently, as shown in FIG. 3B, a p-electrode 140 is formed on
the p-type nitride semiconductor 115 of the light emitting structure 110.
Preferably, the p-electrode 140 is formed so as to serve as an electrode
and a reflecting film.

[0043]Then, as shown in FIG. 3C, a bonding layer (not shown) for bonding a
structure support layer through an eutectic bonding method is formed on
the p-electrode 140, and high temperature and pressure is applied to the
bonding layer so as to perform a bonding process for bonding the
structure support layer 160 on the p-electrode 140. Since the structure
support layer 160 is to serve as a support layer and electrode of a
finalized LED, the structure support layer 160 is formed of a silicon
substrate having excellent heat conductivity and conductance.

[0044]The bonding layer may be formed of gold (Au) or an alloy containing
Au (for example, AuSn).

[0045]Next, as shown in FIG. 3D, the substrate 100 is removed through an
LLO process. In the LLO process, when an energy of about 700 mJ/cm2
is applied at the normal temperature in an arrow direction, the energy is
absorbed at the interface between the substrate 100 and the light
emitting structure 110 such that the bonded surface of the light emitting
structure 110 is thermally discomposed, and the substrate 100 and the
light emitting structure 110 are then separated from each other.

[0046]Then, a photoresist pattern (not shown) for defining a desired size
of unit LED elements is formed on the n-type nitride semiconductor 112.

[0047]Continuously, as shown in FIG. 3E, the light emitting structure 110
is isolated into unit LED elements by a drying etching process using ICP
(Inductive Coupled Plasma) or an isolation (ISO) process using laser,
with the photoresist pattern being set to an etching mask, and the
photoresist pattern is then removed.

[0048]Next, as shown in FIG. 3F, an n-electrode 170 is formed on each of
the n-type nitride semiconductor layers 112 of the isolated light
emitting structures 110, thereby forming the vertical LED.

[0049]In this embodiment, the ISO process for isolating the light emitting
structure into unit LED elements is performed after the LLO process for
separating the sapphire substrate. Therefore, it is possible to prevent
the damage of the light emitting structure such as cracks which have
occurred due to an impact of laser during the LLO process in the related
art.

[0050]Meanwhile, as shown in FIG. 4, after the light emitting structure
110 is isolated into unit LED elements, that is, the process of FIG. 3E
is performed, an insulating film 200 may be formed on the side surfaces
of the isolated light emitting structures 110. The insulating film 200
may be omitted depending on the characteristic of LED and a process
condition. In this case, a reflecting film may be formed instead of the
insulating film 200, depending on the characteristic of LED. FIG. 4 is a
process diagram for explaining the modification of the method of
manufacturing a vertical LED according to the first embodiment of the
invention.

Second Embodiment

[0051]Referring to FIG. 5, a method of manufacturing a vertical LED
according to a second embodiment of the invention will be described. The
descriptions of the same construction as that of the first embodiment
will be omitted.

[0052]FIG. 5 is a process diagram for explaining a method of manufacturing
a vertical LED according to a second embodiment of the invention.

[0053]The method of manufacturing a vertical LED according to the second
embodiment is performed in almost the same manner as the first
embodiment. As shown in FIG. 5, however, the method of manufacturing a
vertical LED according to the second embodiment further includes the step
of forming buffer films 300 on portions of the surface of the p-type
nitride semiconductor layer 115 corresponding to element isolation
regions, before the p-electrode 140 is formed on the p-type nitride
semiconductor layer 115.

[0054]In this embodiment, the ISO process for isolating the light emitting
structure into unit LED elements is performed after the LLO process for
separating the substrate, like the first embodiment. Therefore, it is
possible to obtain the same effect as that of the first embodiment.

[0055]Preferably, the buffer film 300 is formed of a non-conductive
material. More specifically, the buffer film 300 may be formed of
photoresist, polyimide, epoxy, or dielectric.

[0056]Since the method according to the second embodiment further includes
the process of forming the buffer films 300, the p-electrode can be more
reliably protected from an impact of laser during the ISO process than in
the first embodiment.

Third Embodiment

[0057]Referring to FIGS. 6A to 6E, a method of manufacturing a vertical
LED according to a third embodiment of the invention will be described.
The descriptions of the same construction as that of the first embodiment
will be omitted.

[0058]FIGS. 6A to 6E are process diagrams sequentially showing a method of
manufacturing a vertical LED according to a third embodiment of the
invention.

[0059]The method of manufacturing a vertical LED according to the third
embodiment is performed in almost the same manner as the first
embodiment. However, the method according to the third embodiment is
different from the first embodiment in that the process of isolating the
light emitting structure 110 into unit LED elements is divided into two
steps, and the LLO process for removing the substrate 110 from the light
emitting structure 110 is performed between two steps.

[0060]More specifically, the method of manufacturing a vertical LED
according to the third embodiment of the invention is performed as
follows. First, the light emitting structure 110 is formed on the
substrate 100, as shown in FIG. 3A of the first embodiment.

[0061]Then, as shown in FIG. 6A, photoresist patterns PR for defining a
desired size of unit LED elements are formed on the p-type nitride
semiconductor layer 11 5 of the light emitting structure 110.

[0062]Subsequently, as shown in FIG. 6B, a first ISO process for isolating
the light emitting structure 110 into unit LED elements is performed
using laser or a drying etching process using ICP, with the photoresist
patterns being set to an etching mask, such that portions of the light
emitting structure 110 corresponding to element isolation regions remain
with a predetermined thickness.

[0063]Next, the photoresist patterns PR are removed.

[0064]Then, as shown in FIG. 6C, the p-electrode 140 is formed on the
surface of the p-type nitride semiconductor layer 115 of each unit LED
element, and the structure support layer 160 is formed on the p-electrode
140.

[0065]Next, as shown in FIG. 6D, the substrate 100 is removed through the
LLO process.

[0066]Subsequently, as shown in FIG. 6E, the remaining portions of the
light emitting structure 110 corresponding to element isolation regions
are removed through a second ISO process such that the light emitting
structure 110 is isolated into unit LED elements.

[0067]Then, as shown in FIG. 3F of the first embodiment, an n-electrode
170 is formed on each of the n-type nitride semiconductor layers 112 of
the isolated light emitting structures 110.

[0068]In this embodiment, the second ISO process in which the light
emitting structure is completely isolated into the unit LED elements is
performed after the LLO process for removing the substrate, as in the
first embodiment. Therefore, it is possible to obtain the same effect as
the first embodiment.

[0069]Although not shown, the method according to the third embodiment of
the invention may further include the steps of: forming a first
insulating film or a first reflecting film on the side surfaces of the
isolated light emitting structures after the first ISO process and
forming a second insulating film or a second reflecting film on the side
surfaces of the isolated light emitting structures after the second ISO
process, depending on characteristics of LED and a process condition.

[0070]According to the present invention, the LLO process for separating
the sapphire substrate from the light emitting substrate is performed
before the ISO process for isolating the light emitting structure into
unit LED elements. Therefore, it is possible to prevent the damage of the
light emitting structure such as cracks caused by an impact of laser
during the LLO process.

[0071]Accordingly, the method according to the invention can enhance not
only the characteristic and reliability of the vertical LED but also the
production yield of the vertical LED.

[0072]Although a few embodiments of the present general inventive concept
have been shown and described, it will be appreciated by those skilled in
the art that changes may be made in these embodiments without departing
from the principles and spirit of the general inventive concept, the
scope of which is defined in the appended claims and their equivalents.